The present embodiments relate to a magnetic resonance tomography (MRT) system that has at least one magnetic coil for creating a magnetic resonance coupled to a circuit arrangement with a plurality of semiconductor power switches that control the current strength of the coil current.
In an MRT system, the magnetic field, through which a magnetic resonance is created in a body to be examined, is generated by a number of magnetic coils. A constant magnetic basic field or B0 field is overlaid with a number of further magnetic fields that, depending on a measurement procedure or sequence carried out, are modifiable in field strength or alignment. Examples for these fields are the gradient fields and the high-frequency alternating field of the body coil. The magnetic coils for generating these adjustable fields may, for example, consume over 10 KW or even over 40 KW of electrical power. In order to be able to switch the coil current used for this quickly enough, semiconductor power switches, such as transistors, are used as switching elements for controlling the current strength of the coil current. In the event of a single power switch alone not being able to conduct the coil current to be switched without becoming thermally overloaded in doing so, an individual magnetic coil may be supplied by a plurality of semiconductor power switches. Each semiconductor power switch of the plurality of semiconductor power switches then switches a part current, respectively, of the overall coil current to be provided. The semiconductor power switches connected in parallel may thus be switched by a control signal of a control module of the MRT system.
Because of the high-frequency alternating fields, with MRT systems, controlling circuit devices such as the control module, for example, and the control lines leading to semiconductor power switches are to be shielded against the magnetic and electromagnetic fields. Otherwise, interference voltages may be induced in the circuit arrangements, and the functional integrity of the MRT system may be adversely affected by this.